Conventionally, as a line image sensor module used for a scanner, a copying machine, or the like, there has been known a line image sensor module which includes a plurality of image sensors outputting image signals in series to a common signal line by using a DC offset as a reference. In the line image sensor module, the output terminals of the respective image sensors for outputting the image signals are commonly connected to the common signal line, and the image signals of the respective image sensors are sequentially output to the common signal line from the head image sensor. The image signals output to the common signal line are sequentially supplied to a signal processing circuit connected to the following stage of the common signal line.
However, the voltage level of the common signal line tends to be attenuated from the level of the DC offset to the ground level, after the completion of the output of the signal from the final image sensor. When the voltage level of the common signal line is attenuated from the level of the DC offset to the ground level, an operation point of the signal processing circuit connected to the following stage of the common signal line tends to be deviated from a signal-processable range. Therefore, there is a concern that the signal processing circuit cannot perform signal processing on the image signal which is received earlier.